This invention relates to an antitheft device for vehicles and more particularly to an improved antitheft device that avoids bypassing or disabling of the antitheft system and which offers a lower cost.
Conventionally, vehicles employ in addition to electronic ignition controls, other ECU operated devices that function to provide antitheft protection. These are generally utilized in conjunction with a special key that has a sending unit that sends an identification code to a unit on the vehicle so that the vehicle can confirm that a licensed or authorized user is attempting to start or operate the vehicle. Although these systems have a high degree of utility, the antitheft system normally uses a control unit or ECU that is separate from the ECU of the ignition system for the vehicle. Thus, there are external connections between the two units. When an external connection is employed, this gives rise to the possibility of a person being able to defeat the antitheft system. In addition it increases the overall cost.
This type of problem can be best understood by reference to FIGS. 1, 2 and 3 which show antitheft systems of the prior art types that are employed with vehicles such as a small vehicle like a motor scooter or motorcycle.
FIG. 1 is a side elevational view of a small vehicle of the type with which the prior art type of antitheft unit has been employed and which is, in the illustrated example, a motor scooter, indicated generally by the reference numeral 11. The motor scooter 11 includes a body frame assembly 12 that rotatably journals a rear wheel 13 and a dirigible front wheel 14, the latter of which is controlled by a handle bar assembly 15. A rider sits on a seat 16 and controls the vehicle from this location.
The vehicle includes a powering internal combustion engine, indicated generally by the reference numeral 17 and which is of the spark ignited type that includes an ignition coil 18 which is controlled by a CDI ignition control unit 19 that includes an ECU that operates on any type of known strategy. The CDI ignition control unit is enclosed within the body frame assembly to improve security.
The unit includes a main switch 21 that is switched by a suitably coded key with the coding being interrelated to an antitheft unit 22, in a manner, which will be described shortly, for controlling the operation of the vehicle 11. The main switch 21 includes an antenna that receives signals from a transponder carried on the key so as to determine if an authorized user is operating the vehicle or not. Alternately the antenna may be mounted elsewhere on the vehicle, preferably enclosed by the body frame assembly 12 for security reasons. An indicator 24 may be mounted on the handle bar assembly 15 so as to be viewed by the operator seated on the seat 16. This shows the antitheft status.
The vehicle also includes a battery 25 that provides electrical power including power for the starting of the engine 17 by means of a starter motor 26 under the operation of the main switch 21.
An alarm 27 is also associated to provide an audible warning under certain conditions as well as a tilt sensor 28 that determines if the vehicle is being moved without an authorized user.
The units shown in FIG. 1 are those, as has been previously noted, of a conventional system and this conventional system generally falls into one of two categories. The first of these categories is shown schematically in FIG. 2 that constitutes a schematic electrical diagram. In this diagram, only the non-grounded terminal of the battery P and its connections to the various components are illustrated. The main switch 21 is positioned in a line L2 that has connection both to the ignition control unit 19 at R1 and via the line L3 and a connection via a connector Q2 to the antitheft unit 22. Thus, when the main switch 21 is closed, both the antitheft unit 22 and ignition unit 19 are enabled. A further line L1 continuously connects the battery 25 and its terminal T to the antitheft unit through a direct connection Q1.
A line from the main line L2 and controlled by the main switch 21 contains a normally open solenoid operated switch 29 which is energized when the antitheft unit 22 determines that a registered user is using the vehicle, in a manner which will be described, and permits energization of the starter motor 26 to provide starting. The ignition unit 19 then supplies electrical power to the coil 18 and an associated spark plug 31 of the engine 17 for permitting its operation.
The antenna 23 will receive a signal from an owner identification device such as a key 32, which has a transponder that outputs a coded signal to the antitheft unit 22 through a connector Q3. As long as the antitheft unit 22 determines that there is an appropriate user, then the antitheft 22 actuates the solenoid switch 29 through a connection Q7 to the line L2 and the engine can be started and operated.
If, on the other hand, there is an attempt to steal the vehicle either by the use of improper key or by the determination by the tilt sensor 28 that the vehicle 11 is being moved by other than an authorized user, then the antitheft unit 22 receives a signal at the terminal Q4 and disables the starter motor 26 by opening the solenoid switch 29. Also, the alarm 27 is sounded and it may be a sound and/or flashing of the turn signals or other units of the vehicle 11. In addition, the antitheft unit 22 outputs a signal to a display or indicator 24 so as to confirm that the operation is either normal antitheft operation or a condition exists where a theft of the vehicle is being attempted. The method by which the attempted theft is determined can be of any suitable type.
The problem with this type of system is that because the antitheft unit 22 and ignition unit 19 are separate, they have a number of external connections between them, which this permits a person to bypass the antitheft unit 22. For example, a thief may bypass the relay operated switch 29 by using a jumper cable L5 (shown in phantom) between the terminals to the starter motor 26 and the terminal Q2 and line L2 downstream of the main switch 21. Then, the vehicle can be operated without permission and can be stolen.
FIG. 3 shows another prior art type of antitheft unit, which also has the disadvantages of failing to provide adequate antitheft protection due to the use of the separate antitheft unit 22 and ignition control unit 19 and associated external terminals. It also has the added cost of requiring two, separate CPUs.
In this construction, the components are basically the same as and thus have been identified by the same reference numerals as applied in FIG. 2. In this arrangement, the main switch 21 is again placed in the line L2 but in this instance, the line L2 is connected only to the antitheft unit 22 through an external terminal Q1. This unit includes an internal switch 41, which connects the electrical power from the line L2 to a terminal R1 of the ignition control unit 19 via an external conductor L5.
When the proper key is utilized, the switch 41 is closed and then the ignition unit is enabled so that the engine 17 can be operated. In this unit, a line L4 goes directly from the line L2 downstream of the main switch 21 to the starter motor 26 so that the starter motor will be energized when the main switch is operated. However if the proper, authorized key is not utilized the engine 17 will not start because the spark plug 31 will not be fired.
With this type of unit, if a theft is detected in any of the known manners including those previously mentioned, the theft alarm 27 is enabled and the ignition control unit is switched off by opening the switch 41. Thus, theft is prevented.
However, again because of the use of the external terminals, a thief can put a jumper line L6 (shown in phantom) between the battery terminal P and the conductor R1 of the ignition control unit and in essence disable the theft prevention.
Thus, it is should be apparent from the foregoing description of the prior art systems where the antitheft unit and ignition unit are separate from each other and controlled by separate CPUs that have external connections to each other, a thief can easily disable the antitheft protection and steal the vehicle.
It is, therefore, a principal object to this invention to provide an improved antitheft unit for a vehicle wherein the theft of the vehicle can be precluded.
This invention is adapted to be embodied in antitheft unit for a motor vehicle that has a prime mover controlled by a CPU function and a theft detection control by a CPU function. The CPU functions are performed in such a way that there are no external terminal connections that can be jumped so that antitheft protection is possible.
In a preferred embodiment, a single CPU performs the CPU functions so that the cost can be reduced.
In further feature of a preferred embodiment, the single CPU performs the CPU functions at different times so that the single CPU can be made simpler and less costly.